Once upon a time, before atrial fibrillation (AF) ablation, atrially driven runs with irregular ventricular response and no visible p-waves were called AF, independent of duration.

In the first decade of the new millennium, the newly established AF ablation community, exploring a variety of ablation techniques, required a consistent and definable end-point to determine ablation success (prior to this it was impossible to determine the most successful strategies as each ablation centre was able to independently define what a successful outcome was. The community was faced with different centres using different definitions of success and claiming wildly varying success rates whilst employing similar ablation techniques). 

In 2007, the HRS/EHRA/ECAS expert consensus (Calkins et al.,2007)  was reached; successful AF ablation was achieved when the maximum residual AF duration post-ablation was <30s. 30 seconds is an arbitrary value, however, this standardised threshold has been successful in guiding the refinement of AF ablation techniques and has improved patient outcomes. Importantly, it should be noted that the primary motivation for adoption of the 30s rule was not for it to be used as a threshold for anticoagulation treatment.

Whilst generally applauded by the electrophysiology community, the 30s rule has been contentious for some, particularly those employed outside the EP speciality. Some clinicians have argued, quite reasonably, that the AF classification criteria pre-2007 should continue to be used, with the clinician responsible for the patient’s care deciding on its clinical relevance/significance.

Thus, the current status quo has a number of issues:

  1. Should ECG recordings be labelled outside of the conventions of the international governing bodies?
  2. What should events of less than 30s with the characteristics of AF be labelled as? The current non-standardised approach is confusing.
  3. Should the threshold of 30s be regarded as a trigger for treatment?

Whilst being far from perfect, at ECG On-Demand, we believe that all members of the UK cardiology community should follow the conventions of the ESC and HRS. To abandon them would mean, we could be talking about different things whilst calling them the same name. All sub-30s AF-type rhythms should be labelled standardly and must leave the reader in no doubt as to what the ECG reporter is trying to bring the reader’s attention to.

At ECG On-Demand, we have decided to adopt the following labelling protocol for clarity:

  • 2 beats of atrial ectopy is referred to as an “atrial couplet”
  • 3 beats of atrial ectopy is referred to as an “atrial triplet”
  • 4 to 10 beats of atrial ectopy is referred to as an “atrial salvo”
  • Sub-30s AF-type rhythms with more than 10 beats are labelled as an “atrially driven run with irregular ventricular response and no visible p-waves”
  • 30s or greater AF-type rhythms are referred to as “atrial fibrillation”

Using the threshold of 30s as a simple trigger for treatment is unsound. The decision to put a patient on a lifetime of anticoagulant therapy, which is not without its risks, should be considered carefully. Setting CHA2DS2-VASc aside, both duration, AF burden and medical history should be weighed. Recent thinking further complicates matters by suggesting that; short runs of AF may not be as clinically relevant as once thought and perhaps anticoagulation/rhythm management should only be considered in patients with no prior history of stroke/TIA where sustained AF of several hours can be proven (Steinberg, O’Connell and Ziegler, 2018). The risks associated with anticoagulation therapy can be tolerated more easily in patients who have suffered previous stroke or TIA?

The above is further supported by data from the ESC Congress 2023 which has shown that even longer periods of device-detected AF (episodes of >6 minutes) do not benefit from anticoagulation, and in fact, patients may be worse off on anticoagulation. This reassures us that the label of AF should not be applied to shorter periods of atrial arrhythmia as there does not appear to be any benefit to patients.

Once issued, we have no control over how our reports are interpreted and how they affect clinical decision-making, with some doctors (particularly non-cardiologists) relying on the text of the report rather than reviewing the printed ECGs. It would be reasonable to expect that anticoagulation will be considered by a doctor in receipt of one of our reports when it is marked as AF. By using a shorter duration of <30 seconds for reporting AF it is possible that doctors receiving our reports may inappropriately use anticoagulation thereby placing patients at risk.

To summarise, the 30s AF rule is problematic to Holter analysis providers serving a broad spectrum of clinicians including; cardiac electrophysiologists, general cardiologists and general practitioners. However, ignoring the rule would probably lead to more confusion. The situation could be improved if sub-30-second AF type events were labelled in a way that the reader was left in no doubt as to what the author was talking about. Generalised catch-all terms such as “non-sustained atrial tachycardia” do not provide sufficient guidance.

ECG On-Demand welcomes all comments whether in agreement or not.

 

References:

Calkins H, Brugada J, Packer DL, Cappato R, Chen SA, Crijns HJ, Damiano RJ Jr, Davies DW, Haines DE, Haissaguerre M, Iesaka Y, Jackman W, Jais P, Kottkamp H, Kuck KH, Lindsay BD, Marchlinski FE, McCarthy PM, Mont JL, Morady F, Nademanee K, Natale A, Pappone C, Prystowsky E, Raviele A, Ruskin JN, Shemin RJ; Heart Rhythm Society; European Heart Rhythm Association; European Cardiac Arrhythmia Society; American College of Cardiology; American Heart Association; Society of Thoracic Surgeons. HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation developed in partnership with the European Heart Rhythm Association (EHRA) and the European Cardiac Arrhythmia Society (ECAS); in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), and the Society of Thoracic Surgeons (STS). Endorsed and approved by the governing bodies of the American College of Cardiology, the American Heart Association, the European Cardiac Arrhythmia Society, the European Heart Rhythm Association, the Society of Thoracic Surgeons, and the Heart Rhythm Society. Europace. 2007 Jun;9(6):335-79. doi: 10.1093/europace/eum120. Erratum in: Europace. 2009 Jan;11(1):132. PMID: 17599941.

Kirchhof, P. et al. (2023) ‘Anticoagulation with edoxaban in patients with atrial high-rate episodes’, New England Journal of Medicine, 389(13), pp. 1167–1179. doi:10.1056/nejmoa2303062. 

Steinberg JS, O’Connell H, Li S, Ziegler PD. Thirty-Second Gold Standard Definition of Atrial Fibrillation and Its Relationship With Subsequent Arrhythmia Patterns: Analysis of a Large Prospective Device Database. Circ Arrhythm Electrophysiol. 2018 Jul;11(7):e006274. doi: 10.1161/CIRCEP.118.006274. PMID: 30002065.